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The root growth of white mustard continued in all treatments in deep soil layers during winter. White mustard reduced soil N content in both experimental years in September (data not shown). In December and March, the early ploughing and control treatments resulted in higher soil N content compared to the other catch crop and tillage treatments in the 0.5-1 m soil layer (Figure 1). The strip tillage and autumn ridge treatments were as effective as the late ploughing treatment for reduction of soil N content despite only half the stand of white mustard in the strip and autumn ridge treatments. The root yield of the sugar beet, N uptake and sugar yield were unaffected by the treatments despite the differences in N availability.
However, the N content of the sugar beet shoot was higher after the early ploughing and
control treatments, which indicated a higher N availability in the deep soil layers for the sugar beets in these treatments.
Figure 1. The inorganic N content (NH4+ and NO3-) in the 2 m soil profile in (a) December and (b) March 2008/09.
Bars show standard errors (n=4). C: control; ST: strip tillage; RT: reduced tillage; EP: early ploughing;
LP: late ploughing; AR: autumn ridges.
4. Conclusion New combined catch crop and tillage systems, such as strip tillage and autumn ridges, can efficiently reduce the potential N leaching without influencing the yield and quality of the sugar beet root. Early ploughing may increase N leaching and spring N availability as catch crops can take up N only for a short period and then start mineralising after the early incorporation.
Acknowledgements This study was funded by the Danish Food Industry Agency, the Nordic Beet Research and the Department of Food Science, Aarhus University.
References Jabro J.D., Stevens W.B., Iversen W.M. and Evans R.G. 2010. Tillage depth effects on soil physical properties, sugarbeet yield, and sugarbeet quality. Communications in Soil Science and Plant Analysis 41, 908-916.
Kristensen H.L. and Thorup-Kristensen K. 2004. Root growth and nitrate uptake of three different catch crops in deep soil layers. Soil Science Society of America Journal 68, 529-537.
Nitrogen Workshop 2012 Effects of overwinter vegetation cover on soil nitrogen supply to spring barley in Ireland Hackett, R.
Teagasc, Oak Park Crops Research, Carlow, Rep. of Ireland
1. Background & Objectives Vegetative cover established after harvest of a cash crop, either by natural regeneration or by sowing a cover crop, and allowed grow over the fallow period, can significantly reduce nitrate leaching by accumulating nitrogen in their biomass (Hooker at al., 2008). When incorporated into the soil before sowing of the next cash crop the accumulated nitrogen can potentially become available to the succeeding crop, thereby reducing the need for fertiliser N applications. Repeated use of cover crops may lead to an increase in soil organic nitrogen which in turn can lead to an increase in soil supply of nitrogen to succeeding cash crops over time (Constantin et al., 2011). A long-term experiment was established to examine the effect of repeated use of different overwinter covers under two cultivation regimes on the amount of nitrate leaching and on productivity of the cash crop. The objective of the current work was to determine effects of different over winter covers, established repeatedly, after 5 to 9 years on the supply of soil nitrogen to a spring barley crop under Irish conditions.
2. Materials & Methods The experiment was initiated in autumn 2002 and the results presented here are from measurements made in 2007 to 2010. The experiment has previously been described by (Hooker et al., 2008).
Briefly a factorial design with two factors and four replicates was used. The factors were overwinter cover (no vegetation cover, natural regeneration, white mustard cover crop) and cultivation type (plough based tillage, reduced tillage). For the plough based system the soil was not disturbed following harvest except for minimal disturbance of the soil surface during sowing of the mustard seed. For the reduced tillage treatments cultivation occurred soon after harvest of the spring barley crop. The bare treatment was maintained free of vegetation using non-selective herbicide. The natural regeneration treatment comprised any plants germinating following harvest of the previous spring barley crop. The mustard cover crop was established by planting white mustard seed (Sinapsis alba) at 10-12 kg seed/ha. In each season any vegetation present on the plots was incorporated into the soil by ploughing on the plough treatments. In the reduced tillage treatment the barley was drilled without prior cultivation such that the majority of the vegetation remained on the surface of the soil. The experiment was carried out on a light free draining soil. Overall plot size was 12 m x 30 m but within each plot a different 2 m x 2 m area was maintained free of fertiliser N in each season but received all other inputs as per standard practice. At crop maturity the barley from an area of 0.5 m2 at the centre of this area was sampled to ground level. Total crop N accumulation (grain + straw) and grain N accumulation were determined. Results were analysed using ANOVA.
3. Results & Discussion Total crop N uptake was taken as a measure of soil nitrogen supply to the crop. A significant effect of cultivation method was detected in 2008 when reduced cultivation had significantly greater crop N accumulation and grain N accumulation than the plough based system. There was no significant interaction between cultivation method and overwinter cover in any season for either of the variables. Therefore means of overwinter cover across cultivation method are presented (Table 1).
Nitrogen Workshop 2012
Overwinter cover had a significant effect on crop N accumulation in 2007, 2008 and 2010 but not in
2009. In the three seasons where a significant effect of overwinter cover was detected the mustard gave a significantly higher crop N accumulation and grain N accumulation compared to both the bare and natural regeneration treatment. There was no significant difference in crop N accumulation between the natural vegetation treatment and the bare treatment in 2007 and 2010, the natural regeneration treatment had higher crop N accumulation than bare in 2008. The mustard treatment increased crop N accumulation by 36.6%, 59.5%, 18.5% and 44.0% compared to the bare treatment for 2007, 2008, 2009 and 2010 respectively. Mustard increased crop N accumulation by 36.2%, 36.4%, 2.8%, and 22.4% in the respective seasons compared to the natural regeneration treatment. In each season where a significant effect was detected over 70% of treatment differences in crop N accumulation were accounted for by differences in grain N accumulation.
4. Conclusion This work highlights that the presence of overwinter vegetation on land destined for spring barley cultivation can increase the supply of nitrogen to succeeding crops of spring barley but the effect is relatively small and inconsistent. This makes reductions in fertiliser inputs as a result of cover crop use difficult to justify. Furthermore it is not clear if the effects of overwinter cover would be evident where fertiliser N was applied.
References Constantin, J., Beaudoin, N., Laurent, F., Cohan, J.P., Duyme, F. and Mary, B. 2011. Cumulative effects of catch crops on nitrogen uptake, leaching and net mineralisation. Plant and soil 341, 137-154.
Coulter B. and Lalor S. (eds.). 2008.Major and micro nutrient advice for productive agricultural crops, third edition.
Teagasc, Johnstown Castle, Wexford, Ireland.
Hooker, K.V., Coxon, C.E., Hackett, R., Kirwan, L. and Richards, K. 2008. Evaluation of cover crop and reduced cultivation for reducing nitrate leaching in Ireland. Journal of Environmental Quality 37, 138-145
Nitrogen Workshop 2012
Effects of soil inoculation with arbuscular mycorrhizal fungi on plant growth and nutrient uptake of some Mediterranean species grown under rainfed field conditions Saia, S., Ruisi, P., Amato, G., Di Miceli, G., Frenda, A.S., Giambalvo, D.
Dipartimento dei Sistemi Agro-Ambientali, Università degli Studi di Palermo, Italy
1. Background & Objectives Low-input farming systems often suffer nutrient deficits that limit plant performance. The symbiosis between plants and arbuscular mycorrhizal (AM) fungi efficiently promotes plant growth and nutrient uptake, especially in growth-limiting environments (Smith and Read, 2008). AM symbiosis seems to be particularly efficient for the acquisition of low-mobility nutrients such as phosphorus (P), magnesium, and zinc, although it traditionally has been considered irrelevant for plant nitrogen (N) nutrition. However, there is increasing evidence that AM symbiosis plays a significant role in plant N capture, especially under conditions of stress (such as water and nutrient stress). These benefits mainly have been observed in pot studies; field studies have often produced contradictory results (Kaschuk et al., 2010). The present work evaluated the effect of a multispecies AM fungi soil inoculum on the biomass uptake of P and N in two cereals, oat (Avena sativa) and barley (Hordeum vulgare), and two legumes, lentil (Lens culinaris) and fenugreek (Trigonella foenum graecum), all grown in the field.
2. Materials & Methods A field trial was conducted under rainfed conditions at Pietranera farm, Sicily, Italy (37°33N – 13°30E, 170 m a.s.l.), on a Vertic Haploxerept. The topsoil (0–40 cm) characteristics were: clay 50%, silt 23%, sand 27%; pH 8.0 (1:2 H2O); 1.27% organic matter; 83 ppm available P; and 0.76‰ total N. The climate of the experimental site is semiarid Mediterranean. The experimental design was a split plot with four replicates. The main treatment was plant species: oat, barley, lentil, and fenugreek. The sub-plot treatment was soil inoculation: the application of a commercial inoculum containing nine species of AM fungi and non-inoculated soil. The previous crop was durum wheat (Triticum durum). In the first week of December 2010 all crops were sown using the seed rate for each plant species that is usually adopted by farmers in the growing environment. No fertilizer was applied and all plots were hand-weeded during the entire crop cycle. In the first week of May 2011, all crops were cut to 2-cm stubble height. Total fresh and dry weights were determined and a subsample was taken and analyzed for total N and P. Root samples were also collected and stained with 0.05% trypan blue in lactic acid. The percentage of root AM infection was measured according to Giovannetti and Mosse (1980). An analysis of variance was performed according to the experimental design.
3. Results & Discussion On average, the addition of AM fungi inoculum to soil significantly increased biomass production (+14.1%) without affecting P and N concentration, thus producing a significant increase in plant P and N uptake (+8.3% and +12.7% on average, respectively; Table 1). Several studies have shown that AM symbiosis can increase plant P uptake in P-limited environments; although our experiment was performed in P-rich soil, we observed a significant increase in P acquisition by plants. Given the low N availability (a result of both low soil N content and N uptake by the field’s prior cereal crop), the observed growth increase in AM-inoculated oat and barley is probably related to increased plant uptake of N as a result of the symbiotic relationship. The effect of AM fungi inoculation on plant N uptake was evident in lentil (+30% compared to the non-inoculated crop),
Nitrogen Workshop 2012
but not in fenugreek. AM symbiosis may have allowed lentil—a slow-growing and low-yield species that usually suffers abiotic stresses such as nutrient and water deficiency (Materne and Siddique, 2009)—to increase its tolerance to biotic and abiotic stresses. This enhanced plant growth resulted in a higher demand for N, which was satisfied through increased N2 fixation. Other studies (Saia et al., 2010) have shown that AM fungi positively affect the N2 fixation of field-grown forage legumes, particularly when grown under drought conditions. We used a genotype of fenugreek that has good tolerance to biotic and abiotic stresses and that gives reasonable yields under low-input cultivation conditions, which may explain why it benefitted less from the AM symbiosis.
4. Conclusion Our results show that soil inoculation with AM fungi increases both growth and nutrient uptake in cereal and legume species typical of the Mediterranean environment to varying degrees among species. From a practical point of view, inoculation with AM fungi can be a valuable option for farmers to improve the sustainability of the agro-ecosystem as it is an environmentally friendly approach for the increase of crop nutrient uptake.
References Giovannetti M. and Mosse B. 1980. An evaluation of techniques for measuring vesicular-arbuscular mycorrhizal infection roots. New Phytologist 84, 489–500.
Kaschuk G., Leffelaar P.A., Giller K.E., Alberton O., Hungria M. and Kuyper T.W. 2010. Responses of legumes to rhizobia and arbuscular mycorrhizal fungi: A meta-analysis of potential photosynthate limitation of symbioses. Soil Biology and Biochemistry 42, 125–127.
Materne M. and Siddique K.H.M. 2009. Agroecology and Crop Adaptation. In: Erskine W., Muehlbauer F., Sarker A.
and Sharma B. (Eds.). The Lentil. Botany Production and Uses. CABI, Wallingford, UK pp. 47–63.
Saia S., Ruisi P., Amato G. and Giambalvo D. 2010. Effects of arbuscular mycorrhizal symbiosis on growth and N2 fixation of Trifolium alexandrinum under late drought-stress conditions. Grassland in a changing world, vol. 15, Grassland Science in Europe, pp. 842–844.
Smith S.E. and Read D.J. 2008. Mycorrhizal symbiosis. Academic Press, San Diego, CA, USA.
Nitrogen Workshop 2012 Effects of storage method on N disappearance and herbage N recovery from solid cattle manure Shah, G.M.a, Lantinga, E.A.a a Organic Farming Systems Group, Wageningen University, P.O. Box 563, 6700 AN, Wageningen, The Netherlands